Physiology Block 3 Week 17 18 Sleep Flashcards
What is sleep?
unconsciousness from which the person can be aroused by sensory or other stimuli.
Required activity
An active process involving characteristic physiological changes in the organs of the body
Highly organized sequence of events that follow a regular, cyclic program each night.
Are sleep, anesthesia, or coma the same?
They do not exhibit the same brain wave patterns characteristic of true sleep
What does sleep deprivation cause in humans?
Impairs cognition
-dec cerebral glucose utilization and blood flow
Nonspecific neural and physiological symptoms
- complaints
- changes in EEG
- increased sensitivity to painful stimuli
Proposed Functions of sleep
- Restoration and recovery of body systems as well as replenish energy stores while repairing itself after periods of energy consumption
- To conserve energy
- -metabolic rate decreases during sleep
- -“sleep = energy used per day’ - REM needed for memory consolidation, reinforcement of learning, and clearing unneeded memories
- Required for brain development and formation of brain synapses
- -high REM in newborns - Discharge of emotions
- -dreaming in REM may provide safe discharge of emotions
- -muscular paralysis prevents acting out dreams
- -regions that control emotions, decision making, and social interaction reduced = relief from stress?
Do species with greater sleep times have higher or lower metabolic rates?
Higher
In humans, do sleep time and metabolic rate stay constant?
No, both decrease with age
How does sleep affect ability to retain/recall information?
humans who get plenty of NREM sleep in the first half of the night and REM sleep in the second half improve their ability to perform spatial tasks and to retain/recall information obtained the previous day
How is arousal assessed?
Electrical activity reflecting activity of neuronal populations and not the activity of individual neurons
How is the electrical activity of awake state characterized?
alpha rhythm of 8 to 13 Hz
5-100 mv wave amplitude
How is the electrical activity of sleep state characterized?
High amplitude and low frequency (0.5 to 4Hz) during stage 3 and 4 sleep
Thought to reflect a slowing and synchronous discharge of neurons.
What is delta sleep?
Deep sleep
Arousal is more difficult than stage 1 and 2, which have theta rhythm 4-7 Hz
During NREM sleep, are the muscles functional?During REM sleep?
NREM: Muscles are function, but activity is low
REM: skeletal muscle activity is absent, but heart, diaphragm, eye muscles, and smooth muscles remain functional
How is REM sleep characterized?
High frequency and low amplitude
Reflect high and desynchronized cortical activity
NREM: Somatic Activity
Few motor events
Body repositioning
REM: Somatic Activity
Paralysis (Tonic)
- post synaptic inhibition of motorneurons
- hyperpolarization of motorneuron membranes
Phasic
- rapid eye movements
- muscle twitches
NREM: CNS Activation
Mean discharge rate of neurons decreased
Cerebral glucose utilization decreased overall
REM: CNS Activation
Mean discharge rate of neurons INCREASED in many regions
- PGO spikes
- Rapid Eye movements
Cerebral glucose utilization increased
Cerebral blood flow greatly increased
Hypnogram: Young Adults
Five 90 minute cycles alternating between NREM and REM sleep with brief arousals
Deepest stage of NREM occur in first part of night
Episodes of REM becomes longer as night progresses
Tonic REM sleep
Periods of sustained postural muscle atonia + bursts of eye movements
Phasic REM sleep
Postural muscle twitches
When do dreams occur?
REM sleep aka paradoxical sleep
Ultradian Rhythm
rhythm occurring within a period of less than 24 hours
Are sleep patterns of children and elderly the same as young adults?
No, they differ
What happens to total sleep time and percent REM sleep with increased age?
They decrease
REM: infants
High percent of REM sleep
The predominance of REM in infants is thought to reflect synaptic and brain development that occur at these ages.
REM: elderly
Fragmented and relatively reduced sleep time in elderly
The pattern in the elderly probably reflects a gradual deterioration with aging (as occurs in all organs) of sleep control mechanisms resulting in multiple sleep problems
What happens if sleep debt not paid? Can caffeine help?
Not meeting sleep needs still allows us to function, but motor and cognitive functions are impaired.
Caffeine cannot substitute for sleep because only counteract some of the effects of sleep deprivation.
-attenuates adenosine receptor activity promoting wakefullness
How is sleep regulated?
2 process model:
Homeostatic process
-the longer the organism is awake, the greater propensity to sleep
Circadian component
-oscillatory process that affects propensity for sleep and waking
Internal Biological Clock
26-hour period–makes us sleepy at night and awake during the day
10,000 neurouns in suprachiasmatic nucleus (SCN) of hypothalamus
- Regulates endogenous biological rhythms and is reset to match the day length by the environmental photoperiod
- mediated by photoreceptors in retina, sending signals to SCN
- pineal gland (SCN controlled) increases melatonin at night = promote sleep
What happens to sleep/wake cycle when removed from environmental cues?
the cycle is lengthened and the individual goes to bed later each night
several days later he is going to bed the same time as the first night
Cues normally maintain 24 hour sleep-wake cycle
In absence of cues, circadian clock has 26.1 hour sleep-wake cycle
As time in awake state increases, what happens to drive to sleep?
Increases
Adenosine
Sleep promoting factor
Levels increase with wakefulness as a result of ATP and ADP breakdown
Attenuating adenosine receptor activity with caffeine promotes wakefulness
Cytokines
Sleep promoting
May explain why diseased conditions result in increased durations of sleep
Serotonin
Wake and Sleep promoting
there is evidence that drugs which block the formation of serotonin results in sustained wakefulness
What wakefulness promoting substances decrease during NREM?
serotonin, norepinephrine, histamine
These normally inhibit cholinergic neurons in the rostral pontine laterodorsal tegmental and pedunculopontine tegmental nuclei (PPT/LDT).
Released from inhibition, initiate and sustain REM sleep.
Lesions in ____ cause?
- -lateral hypothalamus
- -2 more caudal sites
- -pontomesencephalic junction
- -spinomedullary junction
Multiple brain sites contribute to the normal sleep-wake cycle
Lateral hypothalamus: narcolepsy
2 more caudal sites: insomnia
Critical role of the pons and medulla in regulating the sleep-wake cycle
Pontomesencephalic junction: comatose
spinomedullary junction: no effect
Ascending Arousal Systems
Ascending projections from brainstem and posterior hypothalamus to forebrain, cortical, subcortical targets
Excitatory inputs from many regions and neurotransmitters
OREXIN neurons innervate ascending arousal system and cerebral cortex
NREM and REM Sleep Pathways
Multiple neurochemicals contribute to initiating and maintaining NREM and REM sleep stages of sleep:
- aminergic inputs inhibit cells in PPT/LDT during W and NREM sleep
- NREM sleep inhibition of arousal systems by GABA and galanin from VLPO
- REM sleep driven by predominantly cholinergic neurons
- Aminergic inputs fall silent during REM sleep, disinhibiting PPT/LDT
- REM sleep produces atonia and descending inhibitory inputs to motor neurons and activates the thalamus
How do the brainstem and hypothalamic circadian rhythm promote wakefulness?
Brainstem:
Increased NE
Increased 5-HT
Decreased ACh
Hypothalamus:
Increased activation of the thalamus and cortex
Increased histamine
Decreased GAMA
How do the brainstem and hypothalmic circadian rhythm result in NREM sleep?
Decreased activation of the thalamus and cortex
Increased GABA
Decreased histamine
How do the brainstem and hypothalmic circadian rhythm result in REM sleep?
REM sleep occurs when reduced norepinephrine and serotonin release inhibition of pontine PPT and LDT cholinergic neurons which activate the REM system
Decreased NE
Decreased 5-HT
Increased ACh
NREM: Blood Flow
Little change in cutaneous, muscular, and mesenteric vascular blood flow
State of resting brain activity, reduced neuronal activity, decreased synaptic transmission, and decreased cerebral metabolism
Cerebral blood flow decreases 5-25%
REM: Blood Flow
Vasodilation in mesenteric and renal vascular beds = increased flow
Vasoconstriction in skeletal muscular and cutaneous vascular bed = decreased flow
State of active brain, increased neuronal activity, and increased cerebral metabolism
Cerebral blood flow increases up to 40%
NREM: Blood Pressure
BP falls 5-15%
REM: Blood Pressure
BP fluctuates–unstable during phasic REM due to phasic vagal inhibition and sympathetic activation
NREM: Peripheral vascular resistance
Unchanged or slightly falls
REM: Peripheral vascular resistance
Decreases due to vasodilation
Hemodynamic changes
Parasympathetic innervation in NREM and REM
HR and CO dec
Cerebral blood flow
- NREM: dec
- REM: inc
Phasic REM
–BP and HR unstable due to phasic vagal inhibition and sympathetic activation
Overall slight decrease in total vascular resistance during sleep
NREM: Ventilation
Small decreases by 0.5-1.5 due to secondary reduction in total volume
Respiratory pattern is stable and rhythmic
REM: Ventilation
Decreases, but not as much as NREM
–mostly seen in phasic REM
Respiratory pattern is irregular
–during phasic
Ventilation/Rrespiration changes
Decrease in ventilation and respiration
Decrease in VCO2 and VO2 during sleep
Metabolism slows at sleep onset and accelerates at 5AM
During sleep, ventilation decreases proportional to metabolism
Increase in PaCO2 due to alveolar hypoventilation
Blunted hypoxic and hypercapnic responses
NREM: Thermal Regulation
Body temp begins to fall at sleep onset
Tend to awake on rising phase of core body temp
Lowest during 3rd NREM/REM cycle
NREM: Sweating and shivering
REM: Thermal Regulation
Body temp begins to fall at sleep onset
Tend to awake on rising phase of core body temp
Lowest during 3rd NREM/REM cycle
REM: no thermoregulation
REM/NREM: Limb Muscles
Muscle Tone
- Awake: Maximal
- NREM: decreased
- REM: very decreased/absent. Atonia of skeletal muscles (except diaphragm)
REM/NREM: Upper Airway muscles
Reduction of dilator muscle (palatal, genioglossal) tone or activity during NREM with further reduction in REM
Increase in upper airway resistance and narrowing of upper airway space
Gastric acid secretion
Circadian rhythm
peaks between 10PM-2AM
No relationship with different sleep stages
Gastric motility
Overall inhibition of gastric motor function during sleep
Growth Hormone
Concentrations peak 90 mins after sleep onset
Higher in men
Duration of 1-3 hours
Sleep deprivation suppresses GH secretion
Parathyroid Hormone
Increased levels during sleep compared to awake state
Peaks between 2AM-4AM
ACTH
Cortisol decreases with sleep onset
Cortisol levels lowest in early part of sleep, higher from 4AM-8AM
Prolactin
Sleep dependent pattern
Highest conc during sleep
Levels begin to rise 60-90 mins after sleep onset
Higher in women
Peaks from 5AM-7AM
Gonadotropic Hormone
During pre-puberty and puberty stages in boys and girls, increase during sleep
Testosterone rise at sleep onset and continue throughout sleep
No clear relationship in FSH and LH
Thyroid Stimulating Hormone
Low in awake state
Inc in the evening
Peak before sleep onset
TSH secretion inhibited by sleep and delcines
Aldosterone
Increased during sleep
Peaks prior to sleep OFFSET
Melatonin
Begins to rise in evening and peaks between 3AM-5AM
Highest levels correspond to lowest core body temp
Antidiuretic Hormone
Episodic secretion
NO RELATIONSHIP to sleep
Which statement below is incorrect regarding REM sleep?
The breathing pattern is less regular than during NREM sleep.
The discharge rate of serotoninergic neurons in the raphe pallidus decreases below wakefulness during REM sleep.
Sweating and shivering do not occur during REM sleep.
Skeletal muscle tone is decreased from wakefulness during REM sleep.
Upper airway muscle activity is less during REM sleep than in the awake state.
All true
Which of the following pattern of changes in central neuotransmitters or neuromodulators is associated with the transition from NREM sleep to wakefulness?
Decrease in norepinephrine, increase in serotonin, increase in acetylcholine, decrease in histamine and decrease in GABA.
Decrease in norepinephrine, increase in serotonin. Increase in acetylcholine, decrease in histamine and increase in GABA.
Decrease in norepinephrine, decrease in serotonin, increase in acetylcholine, increase in histamine and increase in GABA.
Increase in norepinephrine, increase in serotonin, decrease in acetylcholine, increase in histamine, and decrease in GABA.
Increase in norepinephrine, decrease in serotonin, decrease in acetylcholine, increase in histamine, and decrease in GABA.
Increase in norepinephrine, increase in serotonin, decrease in acetylcholine, increase in histamine, and decrease in GABA.
Regarding hemodynamic changes that occur from wakefulness to different stages of sleep, all of the below occur except:
During phasic REM sleep, blood pressure and heart rate are unstable due to phasic vagal inhibition and sympathetic activation.
Cerebral blood flow decreases in NREM and increases in REM sleep.
There is a decrease in total peripheral resistance from wakefulness to NREM sleep.
The sympathetic system dominates over the parasympathetic system during NREM and REM sleep.
During REM sleep, there is vasoconstriction of muscular vascular beds decreasing blood flow below NREM sleep.
The sympathetic system dominates over the parasympathetic system during NREM and REM sleep.
